“The Sing-Off” (8 p.m., NBC): It’s time to face the music as the final three groups find out which of them will claim the $100,000 grand prize and a recording contract.

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“The Great Christmas Light Fight” (9 p.m., ABC): The winner of this high-watt decorating contest is crowned tonight and gets $50,000, which should be just enough to pay off their electric bill.

“Major Crimes” (9 p.m., TNT): Jon Tenney reprises the role of FBI agent Fritz Howard from “The Closer” in this new episode that has the team investigating the murder of a wealthy graduate student in a gang-riddled neighborhood.

DirecTV Now has some attractive features, including its price, but the overall service is disappointing and an inadequate substitute for a traditional pay TV package, Tech Files columnist Troy Wolverton says.